The present invention relates to a carrier element having one or more integrated circuits to be incorporated into an indentity card, comprising a substrate having on its surfaces a plurality of contact areas which are connected via connector paths to the corresponding terminals of an integrated circuit disposed in an opening in the substrate or on the substrate, a casting compound surrounding at least the integrated circuit and protecting it from mechanical stresses, and a frame limiting the casting compound.
Such carrier elements are incorporated, for example, into identity cards, credit cards, accounting cards and the like.
For efficient and thus inexpensive production of these cards, a primary product is preferably used having one or more integrated modules mounted on a carrier provided with conductor paths. During production of the card this so-called "carrier element" is inserted into a matching opening in a card. In order to allow for a sufficiently firm seat of the carrier element in the card opening when incorporated into the card, the carrier element is fixed in the opening with an adhesive.
It is already known in this connection (EP-A1 201 952) to provide carrier elements with a contact adhesive layer for their attachment to an indentity card. Each carrier element consists of a substrate provided with the contact adhesive layer, an IC module on the substrate being connected to contact areas via conductor paths (gold wires). The individual layers of the carrier element are produced from endless films. The contact adhesive layer is provided with a protective layer as usual. The contact adhesive layer and protective layer cover the carrier element except for the area in which the IC module and conductor paths are located. Before the carrier element is incorporated into a card, the protective layer is removed from the contact adhesive layer.
In order to protect the circuit and conductor paths from chemical influences, the carrier elements, while they still exist in an endless format, are sprayed over a large area with a varnish layer that is 10 to 50 microns thick and evenly covers the IC module, the conductor paths and the protective layer.
Using the proposed method, the carrier elements can fundamentally be sprayed only with a very thin varnish layer, since the method involves the varnish layer also covering the protective layer, that is is to be removed subsequently. If the varnish layer is thicker, the removal of the protective layer inevitably damages the varnish layer in the area of the conductor paths and thus the conductor paths themselves.
The known proposal can therefore achieve sufficient protection against chemical influences, but it by no means provides sufficient protection against mechanical stresses for the IC module and conductor paths, which are exposed to frequent bending and compressive stresses both during production and during use of the card. In order to achieve effective mechanical protection in this respect, other measures must therefore be taken.
European laid-open print 0 107 061 describes, for example, a carrier element consisting of a film provided with conductor paths. To allow for the IC module to be contacted using customary wire connections without the required card thickness being exceeded, the IC module is mounted in a punched hole in this film. To protect the elements sensitive to mechanical stresses, an annular limiting body is additionally applied here to the upper side of the film, said body enclosing the IC module and the wire connections and being filled with a resin. After the resin has cured, the upper side of the limiting body is ground off together with the resin compound, to make it possible to obtain the required thickness of the card to be produced.
This known proposal is mainly disadvantageous in terms of an inexpensive production of a carrier element since a frame must be applied in a separate and additional working step to prevent the curing casting compound, that must be applied to the IC module for purposes of protection, from flowing out. On the other hand, a limiting element is necessary for limiting the casting compound to a definite area and allowing it to be applied in a predetermined thickness to the elements to be protected. If there is no limiting element, the casting compound can be applied to the parts to be protected, if at all, only with excessive thickness. Before the carrier element is incorporated into an identity card with a predetermined thickness, the excess casting material must be removed, for example ground off.